Linux Sees A Slew Of Point Releases Due To That Nasty IBM POWER9 Vulnerability

Written by Michael Larabel in Linux Kernel on 22 November 2020 at 07:40 AM EST. 20 Comments
Greg Kroah-Hartman has issued new point releases for all of the Linux kernel series he is still maintaining as a result of that IBM POWER9 processor vulnerability plus other random fixes that have accumulated.

Made public on Friday was that IBM POWER9 processor vulnerability whereby the L1 data cache needs to be flushed when crossing privilege boundaries. To fend off the potential and improper leakage of L1 data if paired with other side channels, the Linux kernel by default is now set to flush the L1d when entering the kernel and on user accesses. As outlined in that prior article there are ways to disable that behavior but that is the new default on POWER9 processors. This is sure to hurt the performance and I'll have up some performance tests soon.

Anyhow, out this Sunday morning are Linux 5.9.10, 5.4.79, 4.19.159, 4.14.208, 4.9.245, and 4.4.245.

The primary changes across all these kernel releases is the POWER L1d flushing on kernel entry and user accesses along with other necessary POWER infrastructure changes. But, yes, a few other random kernel fixes tossed in too.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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